Other Assets - Narrative (Details)	1 Months Ended		12 Months Ended
	Jan. 31, 2013 USD ($) building property	Apr. 30, 2012 USD ($)	Dec. 31, 2016 USD ($) building	Dec. 31, 2015 USD ($) building	Dec. 31, 2014 building property
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total real estate mortgage receivable included in other assets, carrying value			$ 8,080,000	$ 8,100,000
Number of properties sold or agreed to be sold | property	3
Number of buildings sold | building	18
Real estate mortgages receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for losses related to real estate mortgages receivable			$ 0	$ 0
Sales of properties resulting in gains and losses | Properties Sold in December
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage financing related to property sold		$ 400,000
Interest rate on real estate mortgage receivable		6.00%
Disposed of by Sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of properties sold or agreed to be sold | property					14
Number of buildings sold | building			62	135	43
Disposed of by Sale | Sales of properties resulting in gains and losses
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage financing related to property sold	$ 7,700,000
Interest rate on real estate mortgage receivable	6.00%